You are what you eat, as the saying goes.

So if recent revelations are anything to go by, and you've ever found yourself chowing down on a beefburger from Tesco, that could make you a... err... horse. Hmm.

A new report by the Food Safety Authority of Ireland (FSAI) has found low levels of horse in beef products sold in Tesco, Lidl, Aldi, Iceland and Dunnes Stores.

According to the FSAI's research one sample of Tesco Everyday Value Beef Burgers showed that the product contained about 29% horse meat (relative to beef).

Scroll down for more food ingredients that might surprise you

Tesco has stated that they have already removed the product from their shelves and are investigating the matter.

Tim Smith, group technical director at Tesco, said: "The safety and quality of our food is of the highest importance to Tesco. We will not tolerate any compromise in the quality of the food we sell. The presence of illegal meat in our products is extremely serious.

"Our customers have the right to expect that food they buy is produced to the highest standards."

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This isn't the first time that the contents of a well-known and widely consumed food product has caused controversy.

Last year international coffee chain Starbucks had to change an ingredient of their Strawberries & Creme Frappuccino drinks, after it was revealed they were using cochineal extract - that's dried and crushed beetles to you and I.

With this in mind HuffPost UK Lifestyle wanted to find out once and for all what other hidden surprises can be found in everyday foods.

From an amino acid found in human hair in bread to wax from sheep's wool in chewing gum, the selection below might be enough to turn your stomach. You've been warned.

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  • Castoreum

    <strong>What it is:</strong> Extract from <a href="http://www.merriam-webster.com/dictionary/castoreum" target="_hplink">beaver perineal glands.</a> <strong>Where you'll find it:</strong> <a href="http://www.huffingtonpost.com/2012/05/11/gross-ingredients-processed-foods_n_1510516.html#slide=967570">"Natural flavoring is defined by the FDA as any substance extracted, distilled or otherwise derived from 'natural' materials, such as plant or animal matter," </a> Bruce Bradley, food industry veteran and food blogger explains. "In the case of strawberry and raspberry flavorings, some natural berry flavors may actually be enhanced by castoreum." It's also sometimes taken (intentionally) in <a href="http://www.webmd.com/vitamins-supplements/ingredientmono-315-CASTOREUM.aspx?activeIngredientId=315&activeIngredientName=CASTOREUM" target="_hplink">supplement form</a>.

  • Lanolin

    <strong>What it is:</strong>Lanolin, also known as wool wax, is a yellow wax-like substance secreted by glands of wool-bearing animals, such as sheep. <strong>Where you'll find it:</strong> <a href="http://www.forbes.com/sites/jennifercohen/2012/04/03/6-disgusting-things-youre-eating-and-you-dont-even-know-it/">Lanolin is found in chewing gum.</a>

  • Gelatin

    <strong>What it is:</strong> Gelatin is made from boiled bones, tendons and skin. <strong>Where you'll find it:</strong> <a href="http://www.peta.org/living/vegetarian-living/animal-ingredients-list.aspx">Fruit gelatins such as jelly and other confectionary goods such as cake.</a>

  • Rennet

    <strong>What it is:</strong> An enzyme found in calves' stomachs. <strong>Where you'll find it:</strong> <a href="http://www.peta.org/living/vegetarian-living/animal-ingredients-list.aspx">In some cheeses.</a>

  • Shellac

    <strong>What it is:</strong> <a href="http://www.health.com/health/gallery/0,,20588763_5,00.html" target="_hplink">Secretions from a bug native to Thailand</a>, Health.com reports. <strong>Where you'll find it:</strong> Coating your favorite shiny sweets, like jelly beans. Look for it on ingredients lists as "confectioner's glaze".

  • L-Cysteine

    <strong>What it is:</strong> An amino acid made from human hair or duck feathers. <strong>Where you'll find it:</strong> Used as a <a href="http://www.huffingtonpost.com/2012/04/24/processed-food-ingredients_n_1441700.html#s890346&title=KFCs_Chicken_Pot" target="_hplink">dough conditioner</a> in some bread products, Bradley says, which can improve the texture and feel of products, as well as prolong their shelf life. <a href="http://www.huffingtonpost.com/2012/05/11/gross-ingredients-processed-foods_n_1510516.html#slide=967570">Michael Doyle, Ph.D., director of the Center for Food Safety at the University of Georgia said</a> that feathers and hair are readily-available waste products that would cost more money to dispose of, and since both are protein, they can be digested down to amino acids.

  • Tuna scrape

    <strong>What it is:</strong> <a href="http://www.npr.org/blogs/thesalt/2012/04/16/150724125/is-tuna-scrape-the-pink-slime-of-sushi">"Tuna backmeat, which is specifically scraped off from the bones, and looks like a ground product."</a> Think the pink slime of the sea. <strong>Where you'll find it:</strong> <a href="http://www.npr.org/blogs/thesalt/2012/04/16/150724125/is-tuna-scrape-the-pink-slime-of-sushi">It has been used to make sushi by some manufacturers.</a>

  • Ammonium Sulfate

    <strong>What it is:</strong> A salt compound <a href="http://www.merriam-webster.com/dictionary/ammonium sulfate" target="_hplink">comprised of nitrogen</a>. <strong>Where you'll find it:</strong> In <a href="http://w3.uwyo.edu/~dwwilson/pamphlet.html" target="_hplink">some fertilizers </a> -- and in some breads, such as the <a href="http://www.subway.com/Nutrition/Files/usProdIngredients.pdf" target="_hplink">rolls at Subway</a>. Chemicals with ammonia are typically added to neutralize a food that's too acidic, says Doyle, which can affect texture. It's safe in the amounts it is used in foods, he says, but admits it will certainly be startling to many people, who may only be familiar with it as a heavy-duty cleaner.

  • Silicon Dioxide

    <strong>What it is:</strong> Also known as silica, it's most often present as <a href="http://dictionary.reference.com/browse/silicon+dioxide" target="_hplink">quartz or sand</a>. <strong>Where you'll find it:</strong> It's added to foods as an anti-caking agent, to keep them from clumping, explains Doyle.

  • Azodicarbonamide

    <strong>What it is:</strong> A <a href="http://www.fao.org/ag/agn/jecfa-additives/specs/Monograph1/Additive-049.pdf" target="_hplink">processing</a> agent <strong>Where you'll find it:</strong> It is found in <a href="http://nutrition.mcdonalds.com/getnutrition/ingredientslist.pdf" target="_hplink">hamburger buns</a>.

  • Cellulose

    <strong>What it is:</strong> <a href="http://online.wsj.com/article/SB10001424052748703834804576300991196803916.html" target="_hplink">Wood pulp</a> <strong>Where you'll find it:</strong> In shredded cheese, salad dressings, chocolate milk and more, according to the <em>Wall Street Journal</em>. It's added to foods to keep them from clumping by blocking moisture, and can <a href="http://online.wsj.com/article/SB10001424052748703834804576300991196803916.html" target="_hplink">thicken foods in the pace of oil or flour</a> (as these are costly ingredients).

  • Cochineal extract

    <strong>What it is:</strong> Dried and crushed cochineal beetles. <strong>Where you'll find it:</strong> <a href="http://www.huffingtonpost.com/2012/04/19/starbucks-beetle-extract_n_1403812.html">Starbucks had to change an ingredient of their Strawberries & Creme Frappuccino drinks, after it was revealed they were using cochineal extract.</a>

What's the weirdest thing you've ever found in your food? Tweet us @HuffPoLifestyle, tell us on Facebook or let us know in the comments below